Some Perspectives on Sensitivity to Initiation of Detonation

High Performance, Low Sensitivity: Conflicting or Compatible?

“…There have, however,b een proposed numerousc orrelations between sensitivity (usually toward impact) and av arietyo fm olecular and crystallinep roperties, including bond energies, bond lengths, bond polarities, electrostatic potentials, NMR chemical shifts, atomic charges, rates of vibrational energy transfer,h eats of fusion, and more. Additionald etails and references can be foundi ns everal overviews [3,28,[36][37][38][39]. These correlations can be quite useful in predicting sensitivities, but they are usually restricted to explosives of aparticular chemical category,s uch as nitramines, nitroaromatics, etc.…”

“…It has been foundt hat C,H,N,O explosives typically feature strongly-positive electrostatic potentialsa bove the central portions of their molecular surfacesa nd above CÀ NO 2 and NÀNO 2 bonds, as well as any hydrogena toms. There are weaker negative potentials around the molecular peripheries due to aza nitrogen atomsa nd the oxygen atoms of NO 2 ,O NO 2 or N-oxide groups [2,7,28,37,39,53,54,58].T his pattern can be seen in Figure 3f or 2,4-dinitro-1H-imidazole (1). In contrast, organic molecules in general frequently have prominent negative potentials, associated for examplew ith lone pairs and p electrons, that may be strongert han the positive ones (note 1H-imidazole (2)inF igure 4).…”

“…Within ag ivenc hemical category( e.g. nitramines), sensitivities tend to be greater as the surface potentials are more positive [2,5,28,37,39,53,54,58,59].W ithin such categories, this can permit estimates of relative sensitivities [60][61][62].P articularly notable is ac omputational study of the 1:1c omplex between CL-20 and TNT,w hich showed that the positive surface potentials of CL-20 and TNT in the complex are weaker and stronger,r espectively, than in the separate molecules [63].T his is consistent with . Calculated electrostatic potential plotted on 0.001 au molecular surface of 1H-imidazole (2).…”

“…Another consequence of the electron-withdrawal that results in the stronglyp ositive molecular surface potentials is that it weakens key bondss uch as CÀNO 2 and NÀNO 2 [39,58,59,68].T his facilitates their ruptures, which may be initiating steps in the chemical decompositions that lead to detonation.…”

“…We have discussed the observed tendency of impact/shock sensitivity to increase with maximumd etonation heat release, with free space per molecule in the crystal lattice and with the strength of the positive electrostatic potential above the central portion of the molecular surface. These are overall trends, not correlations.S ince sensitivity is affected by all three of these factors, and perhaps others, we cannot normally expect it to correlate well with any one of them alone unless the effectso ft he other factors are essentially constant (as is the case for the correlations that have been reported for limited groups of compounds of ag iven chemical type [ 3,28,[36][37][38][39]).…”